Brainstem gliomas consist of a heterogenous group which vary greatly in histology and prognosis.
It should be noted that if not otherwise specified the term brainstem glioma usually refers to the most common histology, the diffuse brainstem glioma.
Brainstem gliomas account for ~25% of all posterior fossa tumours and are most common in children between 7 and 9 years of age 5. There is no recognised gender or racial predilection.
Brainstem gliomas are also recognised in adults, although they are rare accounting for only 2% of adult brain tumours 7. They typically occur in younger adults (third and fourth decade) and tend to be of low grade (WHO I or II) 7.
Although the exact presentation will vary according to location and size of the tumour, in general patients will exhibit a combination of 4:
- cranial nerve palsies
- long tract signs
The duration of symptoms is usually much shorter in diffuse gliomas, in which the history is typically very short (a few days) 4. Additionally, diffuse gliomas more frequently have multiple cranial nerve palsies.
Recognised histological types include:
- diffuse astrocytoma
- usually fibrillary astrocytomas
- WHO grades II-IV
- grade does not impact on prognosis, and thus biopsy is usually not necessary
- focal glioma
- (dorsally) exophytic glioma 4,6
- low grade astrocytoma
NF1 associated brainstem glioma
- seen in up to 9% of NF1 patients
- most frequently seen in the medulla
- appears similar to a sporadic focal brainstem glioma but has an even better prognosis, with little if any progression
The most frequently used classification system is to divide these tumours into four types 5:
- diffuse brainstem glioma
focal brainstem glioma
- tectal plate glioma
- other focal gliomas
- (dorsally) exophytic
- probably an artificial group made up of the downward extension of true brainstem gliomas or upward extension of upper cervical cord intramedullary spinal cord tumours 5
As a general rule mesencephalic tumours tend to be of a lower grade than those in the pons and medulla 3.
- most common location
- classic location for the childhood 'brainstem glioma' which tends to refer to a diffuse pontine glioma
- focal dorsally exophytic brainstem glioma is an uncommon variant accounting for only 10% of pontine tumours, and has a much better prognosis, as it usually represents a pilocytic astrocytoma
- overall survival of pontine gliomas is 10% at 5 years
- least common location
- includes focal dorsally exophytic, focal, diffuse and cervicomedullary junction variants
- cervicomedullary junction tumours usually represent upper cervical tumours extending superiorly
- most common location for NF1 associated tumours
MRI is the imaging modality of choice. The appearance will vary with the tumour type, thus please refer to individual articles.
May show anterior displacement of the basilar artery.
Treatment and prognosis
Again, both treatment and prognosis are significantly influenced by tumour type, morphology and location. Radiation is a key part of treatment.
As a general rule, dorsal exophytic tumours and cervicomedullary tumours tend to do best with surgery, whereas surgery has no role in the management of diffuse brainstem gliomas.
- terrible prognosis
- 90-100% patients die within 2 years of diagnosis 6
- focal (tectal glioma)
- excellent long term survival with CSF shunting (essentially benign lesions)
- focal (other)
- good long-term prognosis with surgery
- (dorsally) exophytic tumours
- good long-term prognosis with surgery
General imaging differential considerations include:
- 1. Koeller KK, Rushing EJ. From the archives of the AFIP: pilocytic astrocytoma: radiologic-pathologic correlation. Radiographics. 24 (6): 1693-708. doi:10.1148/rg.246045146 - Pubmed citation
- 2. Barkovich AJ. Pediatric neuroimaging. Lippincott Williams & Wilkins. (2005) ISBN:0781757665. Read it at Google Books - Find it at Amazon
- 3. Greenberg MS. Handbook of neurosurgery. George Thieme Verlag. (2006) ISBN:313110886X. Read it at Google Books - Find it at Amazon
- 4. Albright AL, Adelson PD, Pollack IF. Principles and practice of pediatric neurosurgery. Thieme Medical Pub. (2007) ISBN:1588903958. Read it at Google Books - Find it at Amazon
- 5. McLone DG, Neurosurgeons AS, Neurosurgery AA. Pediatric neurosurgery, surgery of the developing nervous system. W B Saunders Co. (2001) ISBN:072168209X. Read it at Google Books - Find it at Amazon
- 6. Keating RF, Goodrich JT, Packer RJ. Tumors of the pediatric central nervous system. George Thieme Verlag. (2001) ISBN:0865778485. Read it at Google Books - Find it at Amazon
- 7. Mehta MP. Principles and Practice of Neuro-Oncology, A Multidisciplinary Approach. Demos Medical Pub. (2010) ISBN:1933864788. Read it at Google Books - Find it at Amazon